Tag: chemistry

Quizzes (490) Questions (9892)

Questions Related to chemistry

Multiple choice chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

In the electrolytic reduction of alumina, the electrolyte is covered with coke powder because, if :

  1. prevents oxidation of aluminium formed

  2. reacts with aluminium forming aluminium carbide

  3. prevents heat loss from electrolyte

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The electrolyte is a molten bath of cryolite and dissolved alumina. Cryolite is a good solvent for alumina with low melting point. The molten electrolyte is maintained at high temperature inside the insulating cell by using high amount of coke powder or dust to prevent the heat loss.

Multiple choice chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

Aluminium is extracted by :

  1. Heating sodium aluminium silicate to a high temperature

  2. Treating cryolite with sodium hydroxide solution under pressure

  3. Heating aluminium oxide with coke in a furnace

  4. The electrolysis of molten aluminium oxide in fused cryolite
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Aluminium is extracted by electrolysis. The ore is first converted into pure aluminium oxide by the Bayer Process and this is then electrolysed in solution in molten cryolite another aluminium compound. The aluminium oxide has too high a melting point to electrolyse on its own. The usual aluminium ore is bauxite.

Multiple choice chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

The electrolyte used in electrolytic refining of impure aluminium is:

  1. $AlF _3 + CaF _2$
  2. $Na _3AlF _6 + CAF _2$
  3. $AlF _3, Na _3AlF _6$ and $CaF _2$

  4. Any aluminium salt is molten state
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The electrolytes are used to reduce melting point and increase conductivity.

$\therefore $ The electrolytes are $AlF _{6} , Na _{3}AlF _{6} , CaF _{2}$.

Multiple choice chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

During electrolysis of aluminium, which of the following substance is used as an electrolyte?

  1. $Al _2O _3$
  2. $Al _2O _3, Na _3AlF _6$
  3. $Al _2O _3, Na _3AlF _6, CaF _2$

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The substance which is used as an electrolyte during electrolysis of aluminium is $Al _2O _3, Na _3AlF _6, CaF _2$.

Multiple choice chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

Anodic product in the electrolytic reduction of alumina:

  1. $CO _2, O _2$
  2. $O _2$
  3. $F _2$
  4. $O _2,F _2$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Ionization of Alumina in Electrolytic refining.

$2Al _2O _3\longrightarrow 6O^{-2}+Al^{3+}$
Reaction at cathode
$4Al^{3+}+12e^{-}\longrightarrow 4Al$
Reaction at anode
$6O^{-2}\longrightarrow 3O _2+12e^-$
$O _2$ is released at anode.